Classic monitor designs?

Yes, that's the phenolic ring tweeter, isn't it? Phenolic because the brown surround is phenol plastic. I think Advent used to make woofers like this.

It's the weapon of choice for repairing AR speakers. IMO, cone tweeters work best with a third order filter, which is a step up from the old first orders most people used.

I messed around with my 8" speakers today:

599660d1487267698-restoring-monitor-audio-r300-bookshelf-speakers-monitor-audio-r300-md-resurrected-cabinet-jpg


I had a 7.5R + 0.68uF Zobel on the SEAS metal tweeter, but I think it sounded too polite. It's better now. Very involving speaker and easy impedance. No nasty breakups at all. This circuit will work with almost ANY well-behaved 8" woofer IMO.
 

Attachments

  • Monitor Audio Current 20092017 Circuit.PNG
    Monitor Audio Current 20092017 Circuit.PNG
    7.1 KB · Views: 1,920
  • Monitor Audio R300-MD 20092017 FR.PNG
    Monitor Audio R300-MD 20092017 FR.PNG
    20.4 KB · Views: 1,905
  • Monitor Audio Current 20092017 Phase.PNG
    Monitor Audio Current 20092017 Phase.PNG
    24.9 KB · Views: 687
That's a decent curve Steve. I read some articles and threads on BW3 and people seem to have favourable experiences with it. However, one has to distinguish between electrical and acoustical slopes, and consider drivers' roll off. Sometimes, an asymmetrical XO works wonders.
On average, a passive BW3 means an increase in component costs.

Indeed, it's a no label phenolic ring tweeter as "drop in replacement" for vintage Marantz, Advent etc.
 
Last edited:
Member
Joined 2014
Paid Member
Those Advent woofers had masonite rings to adapt roughly 10" cones to 12" frames. Same colour as phenolic. HK's way to put a large motor with a smaller cone. Remember this is the same guy who had only those parts of the baffle painted that might show through the grill cloth. Not a speaker-porn guy, Henry Kloss.
By the way, those phenolic tweeters are a good match for many old speakers that actually had phenolic tweeters, though there is a large spike at the bottom of it's range which not all old crossovers are set up to deal with. Other than that spike(which the ARs had), however, it is not a replacement for an AR4x. I have here an AR4x tweeter which has come apart. I'll photograph an autopsy sometime, but it is an almost 3" cone, rather than the 3/4-1" cone in the phenolics. It's very weird. There is light cotton-like fuzz betwixt cone and backing plate,fiberglass in the dustcap, and some funny silicone-like gel(not sticky,but soft)on top of the pole piece. I am waiting for the second of a pair of 4xs and hopefully the other tweeter is intact, and can be tested.
I do remember(through the haze of two-score plus years) that the AR4xs sounded more balanced at very high levels than at moderate ones. Never blew up a tweeter, though. A good first speaker for many of us back then.
 
Last edited: